(Unicode C++) PC/SC Wait for Smart Card Status Change (Inserted, Removed from Reader, etc.)

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Demonstrates how to synchronously wait for a status change, such as for a smart card to be inserted into a reader, or removed from a reader.

Note: This functionality was introduced in Chilkat v9.5.0.87.

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#include <CkSCardW.h>
#include <CkJsonObjectW.h>
#include <CkStringBuilderW.h>
#include <CkStringTableW.h>

void ChilkatSample(void)
    {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkSCardW scard;

    // First establish a context to the PC/SC Resource Manager
    bool success = scard.EstablishContext(L"user");
    if (success == false) {
        wprintf(L"%s\n",scard.lastErrorText());
        return;
    }

    // First we'll examine the state of all connected readers to see which have smartcards already inserted..
    // Get JSON containing information about the smartcards currently inserted into readers.
    // This also includes information about USB security tokens.
    CkJsonObjectW json;
    success = scard.FindSmartcards(json);
    if (success == false) {
        wprintf(L"%s\n",scard.lastErrorText());
        return;
    }

    // When writing this example, I have 3 smart card readers plugged into my system.
    // One of them has a smart card inserted.
    // Here's the JSON returned by FindSmartcards...

    // {
    //   "reader": [
    //     {
    //       "name": "Alcor Micro USB Smart Card Reader 0",
    //       "state": "empty"
    //     },
    //     {
    //       "name": "Generic Smart Card Reader Interface 0",
    //       "state": "present",
    //       "vendorName": "Generic",
    //       "serialNumber": "3230303730383138303030303030303030",
    //       "systemName": "Generic Smart Card Reader Interface 0",
    //       "card": {
    //         "atr": "3BFC180000813180459067464A00641606F2727E00E0",
    //         "windows": {
    //           "miniDriver": "tagliov70px.dll",
    //           "cryptoProvider": "Microsoft Base Smart Card Crypto Provider",
    //           "keyStorageProvider": "Microsoft Smart Card Key Storage Provider"
    //         }
    //       }
    //     },
    //     {
    //       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
    //       "state": "empty"
    //     }
    //   ]
    // }

    json.put_EmitCompact(false);
    wprintf(L"%s\n",json.emit());
    wprintf(L" \n");

    // We can iterate over the JSON to find the readers with a smart card already inserted..
    const wchar_t *name = 0;
    CkStringBuilderW sbState;

    int i = 0;
    int count_i = json.SizeOfArray(L"reader");
    while (i < count_i) {
        json.put_I(i);
        name = json.stringOf(L"reader[i].name");

        sbState.Clear();
        json.StringOfSb(L"reader[i].state",sbState);

        if (sbState.Contains(L"present",true) == true) {
            wprintf(L"%s has a smart card inserted.\n",name);
        }
        else {
            wprintf(L"%s does not have a smart card inserted.\n",name);
        }

        i = i + 1;
    }

    wprintf(L" \n");

    // Now let's begin the code to wait for a change (where a smart card gets inserted or removed)

    // Get the list of all readers.
    CkStringTableW stReaders;
    success = scard.ListReaders(stReaders);
    if (success == false) {
        wprintf(L"%s\n",scard.lastErrorText());
        return;
    }

    // Show the reader names..
    int numReaders = stReaders.get_Count();
    i = 0;
    while (i < numReaders) {
        wprintf(L"%d: %s\n",i,stReaders.stringAt(i));
        i = i + 1;
    }

    // Sample output from the above loop.
    // 0: Alcor Micro USB Smart Card Reader 0
    // 1: Generic Smart Card Reader Interface 0
    // 2: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
    // 

    // Synchronously wait 30 seconds for a card to be inserted or removed from any of the above readers.
    CkJsonObjectW json2;
    success = scard.GetStatusChange(30000,stReaders,json2);
    if (success == false) {
        wprintf(L"%s\n",scard.lastErrorText());
        return;
    }

    wprintf(L" \n");

    // Let's see what happened...
    json2.put_EmitCompact(false);
    wprintf(L"%s\n",json2.emit());
    wprintf(L" \n");

    // This is what json2 contains.
    // A card was inserted into the reader named "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0"
    // The "numChanged" indicates that one reader's status changed.  
    // The "changed":true indicates the reader that changed.   The state is now "present".

    // {
    //   "numChanged": 1,
    //   "reader": [
    //     {
    //       "name": "Alcor Micro USB Smart Card Reader 0",
    //       "changed": false,
    //       "state": "empty"
    //     },
    //     {
    //       "name": "Generic Smart Card Reader Interface 0",
    //       "changed": false,
    //       "state": "present",
    //       "atr": "3BFC180000813180459067464A00641606F2727E00E0"
    //     },
    //     {
    //       "name": "SCM Microsystems Inc. SCR33x USB Smart Card Reader 0",
    //       "changed": true,
    //       "state": "present",
    //       "atr": "3BDF96FF8131FE455A018048494443313158587300011B09"
    //     }
    //   ]
    // }

    // Find the reader that changed...
    bool changed;
    const wchar_t *state = 0;
    const wchar_t *atr = 0;

    int numChanged = json2.IntOf(L"numChanged");
    wprintf(L"number of readers with a changed state: %d\n",numChanged);

    i = 0;
    count_i = json2.SizeOfArray(L"reader");
    while (i < count_i) {
        json2.put_I(i);
        changed = json2.BoolOf(L"reader[i].changed");
        if (changed == true) {
            name = json2.stringOf(L"reader[i].name");
            state = json2.stringOf(L"reader[i].state");

            wprintf(L"Changed: \n");
            wprintf(L"    reader name: %s\n",name);
            wprintf(L"    new state: %s\n",state);

            // If a card is now in this reader, we should have the ATR of the card..
            if (json2.HasMember(L"reader[i].atr") == true) {
                atr = json2.stringOf(L"reader[i].atr");
                wprintf(L"    ATR of card inserted into this reader: %s\n",atr);
            }

        }

        i = i + 1;
    }

    // The output from the above loop:

    // number of readers with a changed state: 1
    // Changed: 
    //     reader name: SCM Microsystems Inc. SCR33x USB Smart Card Reader 0
    //     new state: present
    //     ATR of card inserted into this reader: 3BDF96FF8131FE455A018048494443313158587300011B09

    // Applications should always release the context when finished.
    success = scard.ReleaseContext();
    if (success == false) {
        wprintf(L"%s\n",scard.lastErrorText());
    }
    }